The Effect of Pollen Limitation on Plant Reproductive Systems and the Maintenance of Sexual Polymorphisms

Insufficient pollination can affect the reproductive output and the rate of outcrossing of individual plants. We use a phenotypic model to explore the effect of pollen limitation on the evolution of plant reproductive systems. Compared to situations without pollen limitation, we show that conditions for the stability of different reproductive systems can change under pollen limitation: hermaphrodites are maintained under a larger set of conditions at the expense of unisexual types, especially males. We also show that trioecy, i.e., coexistence of hermaphrodites, males and females, can be evolutionarily stable, which is not the case in the absence of pollen limitation.